The present invention relates to a new and improved construction of an electrically insulating plastic element or part employed for an electrical switching device and to the use of this plastic element as a blast nozzle of a gas-blast switch. The plastic element is exposed to the action of arcs and contains a filler which absorbs electromagnetic radiation.
It is already known from German Pat. No. 1,281,528 and British Pat. No. 1,007,486 that the parts of electrical switching devices exposed to the action of arcs experience an undesired high wear. To avoid this drawback it therefore has already been proposed to provide these parts with a lining which is rendered opaque by a filler.
Furthermore, it is known from Swiss Pat. No. 596,641 to add a filler absorbing electromagnetic radiation to the plastic which is employed for the part or element exposed to the action of the switching arcs.
With these heretofore known solutions the filler is capable of preventing that the radiation emanating from the arcs will deeply penetrate into the lining or the plastic part, as the case may be. Yet, the heretofore employed fillers or filler materials are not capable of sufficiently holding back this radiation in order to prevent destruction of the part or element. Under the action of the radiation, which even only slightly penetrates, there occurs a decomposition of the material directly below the surface of the plastic element or part, and such, in turn, causes the formation of hollow spaces or voids. By virtue of the high electrical fields there occurs within such hollow spaces or voids a glow which causes further destruction of the plastic and a splitting-off of parts of the surface of the plastic element.